I actually think it's an interesting question.
Would going to an 18 game schedule change how teams think about using their best players?
Today, we assume that the stars start weekly and we've been assuming that since the days of a 12 game regular season plus one Playoff game schedule.
In general, teams started playing 13 games a season in 1925. From 1937 to 1945, including the War years, the NFL reverted to an 11 game regular season schedule and actually only played 10 games in 44 and 45. The 12 game schedule wasn't set in stone in the NFL until 1947. The NFL schedule remained at 12 games until 1961 and only moved to 14 games around the time of the merger, mimicking the AFL. Division and Conference Championship games weren't introduced until 1967. The season didn't expand to 16 games plus the Wildcard round until 1978.
So, over the years, the "maximum" NFL season has ranged from as few as 11 games to today's maximum of 20, with a proposal that it now go to 22.
While equipment and conditioning have dramatically improved since the days of yore and while the in season bye week probably helps a bit (depending on when it occurs), we're still talking about human flesh and bones and muscle.
So, I think it's reasonable to wonder whether the current model, where everybody plays as long as they can lace 'em up and walk between the lines, is necessarily the right model for a 22 game season and whether resting star starters for a game or two a season wouldn't, under those circumstances, be such a bad idea.
I really had never thought about it before and honestly don't know where I'll come down on the topic, but it seems like a valid subject for discussion and I'm not ready to dismiss it offhand.